Ignition distributor cap with isolated capacitor and resistor

ABSTRACT

The ignition distributor cap comprises an insulating body carrying an input terminal and a series of output terminals for successive contact by a rotor arm of the distributor. A connector forms with the input terminal a capacitor the dielectric of which is the material of the body. A resistor is connected to one of the output terminals and to a further connector.

United States Patent 1 J ukes [4 1 Aug.7, 1973 IGNITION DISTRIBUTOR CAP WITH ISOLATED CAPACITOR AND RESISTOR Norman Allred Jukes, Walsall, England Assignee: Joseph Lucas (Industries) Limited,

Birmingham, England Filed: May 22, 1972 Appl. No.: 255,482

lnventor:

Foreign Application Priority Data July 12, 197] Great Britain 27,661/7] u.s. Cl. 200/19. DC

Int. Cl. .L I-I0lh l/58 Field of Search .Q; 200/19 DC References Cited UNITED STATES PATENTS l2/I944 Zoerlein et al 200/19 DC FOREIGN PATENTS 0R APPLICATIONS 1,184,879 2/1959 France 200/19 DC Primary Examiner-LR. Scott Attorney-John C. Holman and Marvin R. Stern 57 ABSTRACT The ignition distributor cap comprises an insulating body carrying an input terminal and a series of output terminals for successive contact by a rotor arm of the distributor. A connector forms with the input terminal a ca pacitor the dielectric of which is the material of the .body. A resistor is connected to one of the output terrninals and to a furtherconnector.

5 Claims, 4 Drawing Figures rue'v.

PATENTED A115 7 I973 SHEET 1 OF 2 IGNITION DISTRIBUTOR CAP WITH ISOLATED CAPACITOR AND RESISTOR This invention relates to caps for ignition distributors, and has for its object to provide such a cap in a form suitable for use in diagnostic equipment for indicating faults.

A distributor cap according to the invention comprises an insulating body part for connection to the distributor, the body part having an input terminal which when the cap is in position engages the rotor arm of the distributor, and a plurality of output terminals, one for each spark plug of the engine, there being further provided a terminal zone in or on the body part and defining with one of the terminals a capacitor having as its dielectric the material of the body part.

Preferably, the capacitor is defined between the terminal zone and the input terminal.

Most preferably, a resistor is connected between one of the output terminals and a further terminal zone on the body.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of an ignition distributor cap according to the present invention,

FIG. 2 is a sectional view of part of a modified distributor cap also according to the present invention, and

FIGS. 3 and 4 are part sectional views of parts of a further form of distributor cap according to the present invention.

1 nector 121 enables the readings obtained at the con- Referring to FIG. 1, a distributor cap includes a molded insulating body 11 having an input terminal 12 and four output terminals 13. The cap is adapted for connection to a connection is completed from an ignition coil by way of the terminal 12 and a spring loaded brush to a rotor arm (not shown) within the distributor body. The rotor arm then completes electrical circuits by way of the output terminals 13 to the spark plugs of the engine in turn.

The body part 11 is moulded with two slots 14 and 15 and within the slots 14 and 15 are blade connectors 16 and 17 respectively. The connectors 16 and 17 are adapted for connection to diagnostic equipment, and the connector 16 forms with the input terminal 12 a capacitor, the dielectric of which is constituted by the material of the body part 11. 1 J I The connector 17 is connected to one of the terminals 13 through a megohm resistor (indicated generally by reference numeral 18). Thus, the diagnostic equipment receives signals indicating the voltage at the input to the rotor,"arm.aThe signal from connection 17- enables the readings obtained at terminal 16 to be related to a known spark plug. v

Referring now toFIG. 2, the ignition distributor cap illustrated therein is similar to that shown in FIG. 1 and comprises an insulating body 111 with an input terminal 1 l2 and four output terminals 113. An annular conductor 116 surrounding the terminal 112 and having a connector leading to the outside of the body 1 1 1 forms with the input terminal 112 a capacitor, the dielectric of which is constituted by the material of the body 1 1 1.

nector of conductor 116 to be related to a known spark plug.

Turning now to FIGS. 3 and 4, the distributor cap illustrated therein is similar to that of FIG. 2 and comprises an insulating body 211 with an input terminal 212 and four output terminals 213 (only one shown). An annular conductor 216 surrounds the terminal 212 and has a connector 225 leading to an electrical plug pin 226 on the body 211. The annular conductor 216 forms, with the input terminal 212 a capacitor, the dielectric of which is constituted by the material of the body 211.

A resistor 217 is located in a recess 218 in the body 211 and is connected to one of the input terminals 1 13 by a conducting plate 219. The resistor 217 is connected via a spring 222 to a conductor 221 which leads to another pin 227 on the body.

In use, the diagnostic equipment is connected by means of a single multi-way electrical socket connector (not shown) engaged with the pins 226 and 227 with suitable provision for weatherprooflng.

Resistors may beprovided for more than just one of the distributor outlet terminals so that the reading related to more than one sparking plug can be obtained.

I claim:

1. A distributor cap comprising an insulating body part for connection to the distributor, said body part having an input terminal which whenv said cap is in position engages the rotor arm of the distributor, a plurality of output terminals, one for each spark plug of the engine, a conductor surrounding one of said terminals and being spaced therefrom by a portion of the material of said body part, a capacitor defined by said conductor and saidone of said tenninals, the dielectric of said capacitor being said portion of the material of said body part, and a further terminal extending from said conductor.

2. The distributor cap as claimed in claim 1, wherein said one of said terminals is said input terminal.

3. The distributor cap as claimed in claim 1, wherein I a resistor is connected between at least one of said output terminals and a further terminal zone in or on said body part.

4. The distributor cap as claimed in claim 1, wherein said conductor is an annular conductor.

5. The distributor cap as claimed in claim 3, wherein said resistor is disposed in a recess in said body part and is retainedin position by a barbed cap carrying the said terminal zone in the form of a connector extending externally of the body part. 

1. A distributor cap comprising an insulating body part for connection to the distributor, said body part having an input terminal which when said cap is in position engages the rotor arm of the distributor, a plurality of output terminals, one for each spark plug of the engine, a conductor surrounding one of said terminals and being spaced therefrom by a portion of the material of said body part, a capacitor defined by said conductor and said one of said terminals, the dielectric of said capacitor being said portion of the material of said body part, and a further terminal extending from said conductor.
 2. The distributor cap as claimed in claim 1, wherein said one of said terminals is said input terminal.
 3. The distributor cap as claimed in claim 1, wherein a resistor is connected between at least one of said output terminals and a further terminal zone in or on said body part.
 4. The distributor cap as claimed in claim 1, wherein said conductor is an annular conductor.
 5. The distributor cap as claimed in claim 3, wherein said resistor is disposed in a recess in said body part and is retained in position by a barbed cap carrying the said terminal zone in the form of a connector extending externally of the body part. 